Minimum Resistivity Research Articles

Electrically Anisotropic Crust From Three‐Dimensional Magnetotelluric Modeling in the Western Junggar, NW China

AbstractAn island arc environment related to intraoceanic subduction or ridge subduction from the Late Carboniferous to the Early Permian has been proposed for the formation of Western Junggar, NW China, situated in the southwest of Central Asian Orogenic Belt. However, the details and consequences of the subduction remain controversial. To further identify the relics of the Late Carboniferous subduction at depth, three magnetotelluric profiles were deployed. Phase tensors, real induction arrows, and three‐dimensional (3‐D) isotropic resistivity models indicate the presence of a 3‐D anisotropic resistivity structure in the crust. Consequently, a 3‐D anisotropic resistivity model was constructed by forward modeling. The 3‐D anisotropic resistivity model contains two azimuthally anisotropic middle‐upper crust anomalies with minimum resistivity striking N90°E at depths of 5 to 20 km, and an azimuthally anisotropic lower crust anomaly with minimum resistivity striking N20°E at depths of 20 to 46 km. The electrically anisotropic anomalies are closely related to relatively high shear‐wave velocities with significant negative radial anisotropy. The anisotropies in the middle‐to‐upper crust and the lower crust are related to the oceanic ridge (N90°E) subduction with a slab window in the Late Carboniferous and the remnant oceanic slab, respectively. The magnetotelluric observations support a NW70° subduction with an intraoceanic ridge‐transform system in the Late Carboniferous and a remnant oceanic slab trapped in Western Junggar.

Doping effects on physical properties of (1 0 1) oriented tin zinc oxide thin films prepared by nebulizer spray pyrolysis method

Transparent conducting tin doped zinc oxide thin films were prepared by nebulizer spray pyrolysis technique for different doping concentrations. The structural properties was investigated using X-ray diffraction analysis which ensured that the polycrystalline nature of the zinc oxide with hexagonal wurtzite structure. The surface properties were analyzed by scanning electron microscope and atomic force microscope. The Energy Dispersive X-ray spectroscopy ensures that the presence of Zn, O and Sn elements in the deposited films. Optical transmissions of the films exhibit for undoped film is 75%, which is improved up to 93% for tin doped films and the optical absorption is below 1.7%. The band gap energy of the films is achieved in the range of 3.54–3.67 eV. From the Hall Effect measurements we observed a minimum resistivity (9.2 × 10−4 Ω-cm) and maximum carrier concentration (7.4 × 1021 cm−3).

Structural, morphological and optoelectronic properties of CdO:Ag films – precursor solution aging effect

ABSTRACTAg-doped CdO (CdO:Ag) thin films were prepared by spray technique using perfume atomizer from fresh and aged (1, 3 and 5 days) starting solutions. The as-deposited films were characterized by X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy and photoluminescence studies. Face-centred cubic structure and decreased crystallite size were observed with aging period of the precursor solution. Transparency and band gap value increase with aging period of the solution. The CdO:Ag film prepared from 3-days aged solution exhibits a minimum resistivity of 0.98 × 10−4 Ω cm. The aged CdO:Ag films exhibit increased figure of merit values. Thus, aging period of the precursor solution strongly influenced the structural, optical and electrical properties of the Ag-doped CdO thin films.

Physical properties of rare earth metal (Gd3+) doped SnO2 thin films prepared by simplified spray pyrolysis technique using nebulizer

Pristine and rare earth (i.e) gadolinium doped SnO2 thin films have been coated on micro-glass substrates with different Gd doping concentration at constant temperature 450 °C by simplified spray pyrolysis technique using nebulizer unit. The variation of doping concentration from 0 to 6 wt.% in the steps of 2 wt.%. Structural, optical, electrical, morphological and photoluminescence properties had been examined as a function of gadolinium doping level. The X-ray diffraction study exposed that all the prepared pristine and Gd doped SnO2 thin films are (110) preferred orientation with tetragonal crystal structure. The observed transmittance of Gd:SnO2 thin film varies between 91–80% in the visible regions. The estimated optical band gap value was initially decreased from 3.79 to 3.74 eV and then it was slightly increased as 3.77 eV with respect to the increase of Gd doping concentrations. Homogeneous surface morphology with polyhedrons like grains without cracks for all the prepared samples was illustrated by SEM studies. EDS spectra confirms that the existence of Sn, O and Gd elements in the 4% Gd doped SnO2 thin film surface. PL results indicates that three emission bands such as ultra violet, blue and green emission peaks at the wavelength of 360, 493 and 519 nm respectively, for all the prepared Gd:SnO2 films. Minimum resistivity (ρ) 7.14 × 10−4 Ω-cm with activation energy (Ea) 0.05 eV, maximum carrier concentration (n) 2.36 × 1020 cm−3 and figure of merit (ϕ) 52.96 × 10−3 (Ω/sq)−1 were obtained for 4% Gd doped SnO2 thin film using Hall effect measurements.

Atomic layer deposition of WNx thin films using a F-free tungsten metal-organic precursor and NH3 plasma as a Cu-diffusion barrier

Tungsten nitride (WNx) thin films were deposited on SiO2 substrates by atomic layer deposition (ALD) using a fluorine- free tungsten metal-organic precursor of tris(3-hexyne) tungsten carbonyl, W(CO)(CH3CH2C ≡ CCH2CH3)3 and NH3 plasma as a reactant at a deposition temperature of 250 °C. Important ALD characteristics, such as self-limiting growth and linear dependency of the film growth on the number of ALD cycles, were obtained with a growth rate of 0.045 nm/cycle. The minimum film resistivity of around ~2800 μΩcm (thickness: ~ 13.3 nm) was stable after 3 days air-exposure, indicating the high stability of these WNx films. Rutherford backscattering spectrometry showed that the N-rich WNx thin films (N/W ratio: ~ 1.56) were deposited with negligible impurities of C and O. Both X-ray diffractometry and transmission electron microscopy analysis showed that ALD-WNx films formed a polycrystalline cubic WN phase with an average grainsize of ~ 6 nm. From scanning Kelvin probe analysis, its work function was determined as 4.79 eV. Detail investigations were carried out after post-annealing of the as-deposited films and formation of metallic-W with significantly reduced sheet resistance was observed upon annealing at and beyond 700 °C. Finally, the ultrathin (~5 nm) ALD-grown WNx film effectively prevented diffusion of Cu even up to 550 °C, promising it as an efficient diffusion barrier material for the Cu interconnect.

Transport properties and electroresistance of manganite based heterostructure

In the present communication, ZnO/La0.7Sr0.3MnO3/Al2O3 (ZnO/LSMO/Al2O3) heterostructure was grown using chemical solution deposition (CSD) technique. X–ray diffraction (XRD) measurement confirms the (100) crystallographic oriented growth of LSMO manganite and polycrystalline hexagonal growth of ZnO layer. Temperature dependent resistivity behavior under different applied magnetic fields, performed for two different geometries [current in plane (CIP) and current perpendicular to plane (CPP)], suggests the modifications in metal to insulator transition temperature TP and alterations in resistivity with applied magnetic field and measurement geometry. This also implies the better charge conduction across the ZnO/LSMO interface (CPP) as compared to LSMO film layer (CIP). Various charge conduction mechanisms have been employed to understand the charge transport for observed low temperature resistivity minimum, metallic behavior, insulating state and magnetoresistance (MR) of LSMO film and ZnO/LSMO interface. Electroresistance (ER) and field effect configuration (FEC) have been investigated across the ZnO/LSMO interface by recording the LSMO channel resistance, at room temperature, that suggest the tuning of signature and value of ER by considering forward and reverse bias modes across the interface. FEC studies show the large ER ∼ +750% and −85% across the LSMO channel with its tunability under different interface biases.

Direct Writing of Copper Micropatterns Using Near-Infrared Femtosecond Laser-Pulse-Induced Reduction of Glyoxylic Acid Copper Complex.

We have fabricated Cu-based micropatterns in an ambient environment using femtosecond laser direct writing to reduce a glyoxylic acid Cu complex spin-coated onto a glass substrate. To do this, we scanned a train of focused femtosecond laser pulses over the complex film in air, following which the non-irradiated complex was removed by rinsing the substrates with ethanol. A minimum line width of 6.1 µm was obtained at a laser-pulse energy of 0.156 nJ and scanning speeds of 500 and 1000 µm/s. This line width is significantly smaller than that obtained in previous work using a CO2 laser. In addition, the lines are electrically conducting. However, the minimum resistivity of the line pattern was 2.43 × 10−6 Ω·m, which is ~10 times greater than that of the pattern formed using the CO2 laser. An X-ray diffraction analysis suggests that the balance between reduction and re-oxidation of the glyoxylic acid Cu complex determines the nature of the highly reduced Cu patterns in the ambient air.

Effects of laser pulse energy on the structural, optical and electrical properties of pulsed laser deposited Ga-doped ZnO thin films

Transparent conducting Ga-doped ZnO (GZO) thin films were deposited on glass substrate by pulsed laser deposition (PLD). The effects of laser pulse energy ranging from 80 to 200 mJ on microstructural, surface morphology, electrical and optical properties of GZO films were investigated in detail. XRD patterns have shown that all samples were hexagonal wurtzite structure presenting predominant orientation along the (002) c-axis direction, and the film obtained at 160 mJ showed the optimal crystallinity. The Raman spectra demonstrate that GZO films have oxygen vacancies, Zinc interstitials, and residual stress. The compact, homogenous and flat surface morphology of GZO films were observed by AFM. Hall effect measurements revealed that the electrical properties of samples were dominated largely by the crystallinity and the minimum resistivity of 6.10 × 10−4 Ω cm was obtained when GZO film grown at 160 mJ. Optical transmission spectra displayed an average transmittance higher than 90.6% for all GZO samples in the visible range. The film deposited at 160 mJ exhibited the maximum figure of merit of 22.70 × 10−3 Ω−1, owing to the low resistivity and high transmittance.

Influence of fluorine doped CdO thin films by an simplified spray pyrolysis technique using nebulizer

The Cadmium oxide (CdO) and Fluorine (F) doped CdO thin films were effectively synthesized on glass substrates for different F doping concentrations (2, 4, 6, 8 at.%) using nebulized spray pyrolysis technique. The XRD analysis showed that all the films were polycrystalline having cubic structure with (111) preferential orientation. It was seen from the SEM photographs that the doping causes remarkable changes in the surface morphology. EDAX analysis clearly confirmed that the presence of expected elements cadmium, oxygen and fluorine in the final product, in appropriate proportions. The electrical study showed that the minimum resistivity value of 1.9 × 10−4 Ω cm with notable higher values of carrier concentration and mobility was achieved for 6 at.% of CdO:F film. Optical study exhibited that the band gap value of CdO film increases gradually with the increase in F-doping concentration, reaching maximum band gap value of 2.61 eV at 6 at.% and starts decreasing thereafter. Photoluminescence spectra depicted that the intensity of the emission peaks was significantly varied with doping concentrations. The high transparency, wide band gap energy, enhanced electrical properties and light sensitivity had been obtained infer that F-doped CdO thin films which find application in optoelectronic applications.

Evaluation of resistivity anisotropy parameters in the Eastern Mitidja basin, Algeria, using azimuthal electrical resistivity tomography

ABSTRACTWe study electrical anisotropy using azimuthal electrical resistivity tomography (A‐ERT) for identifying geological layers and determining the preferential aquifer flow direction. The work presented in this paper aims at calculating the anisotropy coefficient from the inverted resistivity measurements, relating the geophysical results to the site geology and water flow direction, and comparing the results with those obtained from prior studies using hydrogeological approaches. The study area is located in the Eastern Mitidja basin, about 15 km east of Algiers. The work carried out includes three measurement points, totalling 24 ERT profiles. For each point, eight A‐ERT profiles, using Wenner–Schlumberger array configuration, were performed every 22.5° around a fixed central point. The data processing includes two‐dimensional inversion of each profile, representation of the inverted resistivities at the central points as a function of the azimuth in polar diagrams, and implementation of an inversion program to determine the best fitting azimuthal anisotropy parameters. The origin of electrical anisotropy is probably due to grain alignment, which is often observed in fine‐grained sediments such as clays and some sands. This alignment creates a higher electrical resistivity perpendicular to the alignment than parallel to it, which is an indicator for higher hydraulic permeability in the minimum resistivity direction, which corresponds to the preferential groundwater flow direction.

UV–vis transparent conducting Ta-doped SnO2 epitaxial films grown by metal-organic chemical vapor deposition

Tantalum (Ta)-doped SnO2 films with different Ta concentrations have been deposited on α-Al2O3 (012) substrates by the metal organic chemical vapor deposition (MOCVD) method at 620 °C. Structural, electrical and optical properties of the obtained films have been investigated in detail. Structural analyses revealed that all the obtained films were rutile SnO2 growing along SnO2 [101] orientation. The 4% Ta-doped SnO2 film exhibited the best crystal quality and the in-plane epitaxial relationship between the film and substrate was SnO2 [010]//Al2O3 [110]. The highest Hall mobility of 58.1 cm2 V−1 s−1 was achieved for the 4 at.% Ta-doped SnO2 film and the minimum resistivity as low as 4.0 × 10-4 Ω cm was obtained at 6 at.% of Ta doping concentration. In the visible light region, all the obtained films showed average transmittances exceeding 88%. With Ta concentration increasing from 0 to 8 at.%, the transparent range of the films extended to the UV-B light region (280–320 nm), while the optical band gap of the films rose from 3.96 to 4.30 eV.

Effects of thermal treatment and layers’ number on SnO2 thin films properties prepared by sol-gel technique

Tin oxide layers are very important in photovoltaic applications. This paper presents an in-depth study of the SnO2 thin films deposited by the gel dip coating technique on glass substrates. The heat treatment and the number of layers effect on structural, morphological, optical and electrical properties were studied. Differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA) showed that SnO2 crystallized at 402.5 °C. The diffraction spectra x-rays revealed that a formation of tetragonal cassiterite structure with a preferred growth orientation according to (101) plane. Exceptional film prepared at 200 °C preheated temperature is according to the (110) plane growth orientation. The size of the crystallites is strongly influenced by the preheated temperature, annealing temperature and a number of layers. The AFM images show homogeneous surfaces for all samples except the film prepared at a preheated temperature of 200 °C. However, it becomes smoother by increasing the number of layers. UV-Visible spectroscopy has shown that greater transparency is found in the infrared and visible domains (75%–96%). For all films, the optical band gap energy varies randomly with the preheated temperature; conversely, it increases from 3.83 eV to 3.88 eV for three-layer and six-layer films respectively. The energy gap decreases for samples with more than 6 layers. The minimum resistivity values are 8.1 10–1 Ω cm determined by the four probe method for the sample preheated to 400 °C without annealing temperature.

The impacts of blanket on CFETR ohmic breakdown

China Fusion Engineering Test Reactor (CFETR) design is under way, it is necessary to develop an optimized scenario for plasma breakdown and current ramp-up, and to evaluate the consequent design constraints. A good initial magnetization (IM) and volt-seconds optimization are carried out for the ohmic breakdown based on the 2D TokSys model, giving the maximum volt-seconds that the magnetic coils can provide. Take IM as the initial condition, the ohmic breakdowns on the conditions that the blanket has different equivalent resistivities and positions are optimized. Comparisons of the optimized values and the target values are made. The ohmic breakdown without blanket is calculated as well, as a reference, the minimum equivalent resistivity of blanket required to meet the breakdown condition is obtained. Both initial magnetization and ohmic breakdown optimization could serve as preliminary references for the CFETR coils and blanket designs.

Growth and characterization of F-doped α-Ga2O3 thin films with low electrical resistivity

F-doped α-Ga2O3 thin films with low electrical resistivity were epitaxially grown on c-plane α-Al2O3 substrates by means of mist chemical vapor deposition. The resistivity of the α-Ga2O3 thin films was decreased dramatically by incorporating F into α-Ga2O3, achieving a minimum resistivity of 6.2 × 10−2 Ω·cm in a 1050 nm thick film grown from a precursor solution with a [F]/[Ga] ratio of 20%. Further, the carrier concentration was 1.3 × 1019 cm−3, and the Hall mobility was 4.6 cm2/Vs with the [F]/[Ga] ratio of 20% and a film thickness of 1560 nm. Secondary ion mass spectrometry revealed that the F concentration incorporated into the α-Ga2O3 thin film was approximately 1 × 1020 cm−3, and the activation ratio was approximately 10%. The higher [F]/[Ga] ratio in the precursor solution caused lower crystallinity, as demonstrated by X-ray diffraction rocking curves. For all [F]/[Ga] ratios, as the film thickness increased to approximately 1000 nm, the electrical resistivity of the thin films drastically decreased. In the thinner films, the dislocations at the interface between the α-Ga2O3 thin films and the α-Al2O3 substrates are thought to trap electrons and compensate the free carriers or deteriorate the mobility.

Electrical resistivity of self consolidating concretes prepared with reused concrete aggregates and blended cements

The current study firstly quantifies the electrical resistivity of Self Consolidating Concrete (SCC) prepared with Coarse Reused Concrete Aggregates (CrRCA) and Fine Reused Concrete Aggregates (FnRCA) at alternate substitutions of Coarse Natural Aggregates (CNA) and Fine Natural Aggregates (FNA) respectively. Secondly, the efficacy of Silica Fume (SF) and Metakaolin (MK) in compensating the loss in the performance of SCC on account of replacement of natural aggregates with recycled aggregates measured in terms of electrical resistivity has been assessed. For assessing the electrical resistivity of the SCC combinations, electrical resistivity tests were executed. The minimum electrical resistivity has been observed for complete substitution of Natural Aggregates (NA) with RA. Relative to the control combination across all curing periods, the electrical resistivity has been declined for substitution of CNA/FNA with CrRCA/FnRCA whereas, with the introduction of either SF/MK, it was enhanced considerably. The electrical resistivity of the SF/MK blended SCC combination prepared with 50% of CrRCA and 100% of FnRCA was noticed to be more than that of the control SCC combination across all curing periods. Based on the outcomes, suggestions have been made for the best combinations of CrRCA, FnRCA and cement additions for the optimum performance of SCC combinations.

High power UVB light emitting diodes with optimized n-AlGaN contact layers

The influence of the n-AlGaN contact layer thickness and doping profile on the efficiency, operating voltage and lifetime of 310 nm LEDs has been investigated. Increasing the n-contact layer thickness reduces the operation voltage of the LEDs and increases the emission power slightly. Optimizing the n-doping profile yielded enhanced conductivity and reduced operation voltage with a simultaneous output power enhancement of the LEDs. Lifetime measurements have shown that even though the output power of the LEDs was enhanced the lifetimes were not negatively affected. Room temperature photoluminescence indicates a low concentration of point defects in the n-doping region yielding minimum AlGaN resistivity.

Effect of oxygen flow rate on the low temperature deposition of titanium monoxide thin films via electron beam evaporation

In this study, titanium monoxide thin films were evaporated by an electron beam source under different oxygen atmospheres at deposition temperatures not exceeding 80 °C. Deposition of thin films at low temperatures is a prerequisite for heat sensitive substrates. XRD results showed that crystallinity of titanium monoxide is achieved without the requirement of high temperature annealing. When oxygen is introduced into the coating chamber, a titanium peak is formed at exactly the Ti+2 position together with a small amount of Ti+3 and Ti+4 peaks. According to XPS analysis, the structure is transformed into mostly the Ti+4 state when the oxygen flow rate is over 25 sccm. The bandgap of thin films increases from 3.0 to 3.8 eV with an increase in oxygen flow rate from 1 to 50 sccm. Both optical transmission and Hall effect measurements showed the change in carrier type from p to n when the flow rate reaches 25 sccm. Electrical resistivity increases with additional oxygen in the structure, and minimum resistivity is obtained as 1.7 × 10−4 Ω cm when no oxygen is admitted into the chamber. Highly conductive thin films were also observed via ultraviolet photoelectron spectroscopy measurements which yield a high density state showing a metallic character with degenerated oxide semiconductor nature.

Understanding the role of glucose oxidase on carbon felt as electrodes in biocapacitor studies

In this work, we have reported glucose oxidase incorporated carbon felt bioelectrodes (GOx/CFE) as biocapacitors for energy storage. Glucose oxidase (GOx) was incorporated into a carbon felt electrode (CFE) and the electrode was characterized using X-ray diffraction, scanning electron microscope and Fourier transform infrared spectroscopy. As a result, it was found that GOx was successfully incorporated into a bare CFE and enhances the specific capacitance of the electrode and it was stable up to 500 charge–discharge cycles. Consequently, it was observed that GOx/CFE exhibits enhanced energy storage capacitance compared to that of pristine carbon felt. The capacitance of GOx/CFE is found to be \(4.21\hbox { mF cm}^{-2}\,(23\hbox { F g}^{-1})\) while the bare CFE shows \(3.68\hbox { mF cm}^{-2}\) in a phosphate buffer solution (\(\hbox {pH}=7.0\)). Albeit the capacitance values are small compared to conventional supercapacitors, the utility of these biocapacitors is expected to have a significant impact on glucose monitoring. Columbic efficiency obtained with the GOx/CFE matrix is 89%, and the electrode is stable up to 225 cycles with 100% retention of capacitance. After 225 cycles, the electrode loses the capacitance up to 12% retaining the capacitance of 88% up to 500 cycles. Cyclic voltammetric studies revealed that GOx/CFE is capable of energy storage with a \(200\,\upmu \hbox {A}\) higher capacitive loop than the bare CFE at a scan rate of \(10\hbox { mV s}^{-1}\). Electrochemical impedance analysis measurements also confirmed that GOx/CFE possess minimum resistivity. Moreover, it is very eco-friendly due to which unwanted pollution can be avoided. From the proposed matrix, it is believed that a green, eco-friendly, clean, renewable material for energy storage could be realized.

Controlling the charge transport mode in permalloy films using oblique angle deposition

Abstract We have systematically studied the effect of oblique angle deposition (OAD) on the transport properties of Permalloy (Ni81Fe19) thin films. Films deposited at oblique angles larger than 50° exhibit a resistivity minimum that can be further manipulated by changing the oblique angle. A minimum in temperature dependent resistivity is manifested as a deviation from the usual phonon-scattering behavior. Furthermore, a change in the magnetic anisotropy in the films is clearly demonstrated in their magnetoresistance that shifts from negative to positive with increasing glancing angle. OAD results in the formation of columns-like microstructures on the films, while their porosity greatly enhances. The microstructural evolution induced by OAD modifies the fundamental electron scattering process in the films. The modifications in the scattering mechanism outcomes in a resistivity minimum in the films grown at high oblique angles. The possible mechanisms responsible for the observed behavior are discussed.

Intergranular fracture prediction and microstructure design

A model based on discrete unit events coupled with a graph search algorithm is developed to predict intergranular fracture. The model is based on two hypotheses: (i) the key unit event associated with intergranular crack propagation is the interaction of a grain boundary crack with a grain boundary segment located at an angle with the initial crack plane; and (ii) for a given crack path, the overall crack growth resistance can be calculated using the crack growth resistance of a collection of unit events. Next, using a directed graph containing the connectivity of grain boundary junctions and the distances between them, and crack deflection versus crack growth resistance data, a directed graph in the J-resistance space is created. This graph contains information on the crack growth resistance for all possible crack paths in a given grain microstructure. Various crack growth resistance curves are then calculated including those corresponding to: (i) a local resistance minimum; (ii) a global minimum; and (iii) for verification, a path specified by microstructure-based finite element calculations. The results show that the proposed method based on discrete unit events and graph search can predict the crack path and the crack growth resistance for cracks that propagate from one grain boundary junction to another. The proposed computationally inexpensive model can be used to design material microstructures with improved intergranular fracture resistance, and/or to assess the overall crack growth resistance of materials with a known distribution of grain morphology.